1. Technical Field
The present invention relates generally to municipal waste processing systems, and relates more specifically to an apparatus for opening garbage bags in a municipal waste processing stream, to liberate the contents of the bags prior to subsequent treatment of the waste.
2. Prior Art
The refuse from individuals and businesses alike frequently is accumulated in plastic garbage bags which are secured closed, in some fashion, and left for pick-up and hauling to disposal sites. For collection and handling of refuse, the plastic garbage bag needs to be burst and tear resistant. If easily burst or torn, the bag may be ripped open by the contents contained therein, either while the contents are being deposited in the bag or while the bag is being carried from one location to another prior to the final pickup for hauling to disposal. Since the refuse contained in a garbage bag will normally include a mixture of hard and soft articles, some with pointed ends or relatively sharp edges, garbage bags are frequently designed to stretch or break slightly, without substantial tearing, and tear propagation is minimized. Frequently the tear strength is sufficient such that the bags are not opened even by the mechanical compaction applied thereto in the final collecting equipment, such as a garbage truck.
When municipalities were allowed to landfill the entire volume of collected municipal waste, the tear or burst resistance of garbage bags was of little or no concern. However, with decreasing capacities in existing landfills, the unavailability of additional landfill sites, the increasing costs for landfill operation and the enactment of environmental laws making recycling desirable and even mandatory, many municipalities have installed municipal waste processing systems which separate the components of the municipal waste for subsequent processing such as burning, recycling, or other handling. In such systems, it is necessary to liberate the contents from containers such as garbage bags, so that the necessary separating and treating steps can be performed on the various different articles in the refuse.
It was common in early municipal waste processing systems to merely shred the municipal waste in hammer mills, or other comminuting devices. The result was that the bags were opened and contents liberated; however, the contents themselves were shredded or pulverized. Pieces of the garbage bags can plug the devices, blind the hammers or other implements and otherwise foul the apparatus, reducing its efficiency.
Trommel screens have also been utilized for liberating contents from garbage bags, which screens comprise a large tilted drum in which the bags are tumbled. While these have been somewhat successful in liberating the contents of the bags, due to the tumbling action, frangile containers break, and all bags are not uniformly opened.
In many present municipal waste processing systems, it is desirable to minimize the degree of shredding which occurs prior to separation. Therefore, it is desirable to provide a garbage bag opening device which will tear the bags for opening and liberating refuse without shredding, crushing or significantly breaking the contents in the bags.
A device intended for gentle garbage bag opening is disclosed in U.S. Pat. No. 4,479,581 "Apparatus and Method for Processing Bagged Refuse" wherein a disk screen is used for bag opening, with a bag breaking means consisting of disk assemblies operating above the screen bed to open the bags. The disks have serrated or toothed edges, to help in bag opening and content liberation. However, since the bags are torn and not shredded, it is common that the large, opened plastic bags will wrap around the disks, thereby limiting future effectiveness of the disks in bag opening. Other types of bag openers suffer similar plugging or blinding problems.
It is, therefore, an object of the present invention to provide an apparatus for opening garbage bags, to liberate the contents of the garbage bags, which is effective in operation to liberate the waste, yet minimizes breaking or size reduction of the liberated material.
Another object of the present invention is to provide a garbage bag opener which is self-cleaning and reduces blinding from the municipal waste contained in a municipal waste stream.
Still another object of the present invention is to provide a garbage bag opener which is not easily damaged by large and hard articles contained in the municipal waste stream and which is simple, yet effective in operation.
Yet another object of the present invention is to provide a garbage bag opener which is inexpensive to build and install and adaptable to different garbage stream conditions.